scholarly journals Expression of the intermediate-filament-associated protein synemin in chicken lens cells.

1984 ◽  
Vol 4 (10) ◽  
pp. 1943-1950 ◽  
Author(s):  
B L Granger ◽  
E Lazarides
Keyword(s):  
Skeletal Muscle ◽  
Intermediate Filaments ◽  
Intermediate Filament ◽  
Early Stage ◽  
Cellular Structures ◽  
Fiber Cells ◽  
The Core ◽  
New Information ◽  
Avian Muscle ◽  
Lens Cells

Synemin, a 230-kilodalton polypeptide component of avian muscle and erythrocyte intermediate filaments, is also found in association with the vimentin filaments of lens tissue. In chicken lens cells, synemin is bound to the core vimentin polymer with the same 180-nm periodicity that it exhibits in erythrocytes. Its solubility properties are characteristic of those of intermediate filaments in general and similar to those of synemin in muscle cells and erythrocytes. Synemin appears at an early stage of lens development and undergoes a dramatic accumulation as the epithelial cells elongate and differentiate into fiber cells. In contrast to synemin in cultured skeletal muscle, lens synemin is not confined to postmitotic, terminally differentiating cells but is present in proliferative cells as well. It is lost from the fibers near the center of the lens, as are many other cellular structures including intermediate filaments. These findings provide new information about the occurrence and expression of avian synemin and new insight regarding its presumptive role as a modulator of intermediate-filament function.

scholarly journals Expression of the intermediate-filament-associated protein synemin in chicken lens cells

1984 ◽  
Vol 4 (10) ◽  
pp. 1943-1950
Author(s):  
B L Granger ◽  
E Lazarides
Keyword(s):  
Skeletal Muscle ◽  
Intermediate Filaments ◽  
Intermediate Filament ◽  
Early Stage ◽  
Cellular Structures ◽  
Fiber Cells ◽  
The Core ◽  
New Information ◽  
Avian Muscle ◽  
Lens Cells

Synemin, a 230-kilodalton polypeptide component of avian muscle and erythrocyte intermediate filaments, is also found in association with the vimentin filaments of lens tissue. In chicken lens cells, synemin is bound to the core vimentin polymer with the same 180-nm periodicity that it exhibits in erythrocytes. Its solubility properties are characteristic of those of intermediate filaments in general and similar to those of synemin in muscle cells and erythrocytes. Synemin appears at an early stage of lens development and undergoes a dramatic accumulation as the epithelial cells elongate and differentiate into fiber cells. In contrast to synemin in cultured skeletal muscle, lens synemin is not confined to postmitotic, terminally differentiating cells but is present in proliferative cells as well. It is lost from the fibers near the center of the lens, as are many other cellular structures including intermediate filaments. These findings provide new information about the occurrence and expression of avian synemin and new insight regarding its presumptive role as a modulator of intermediate-filament function.

Molecular analysis of intermediate filament cytoskeleton--a putative load-bearing structure

1984 ◽  
Vol 246 (4) ◽  
pp. H566-H572 ◽  
Author(s):  
M. G. Price
Keyword(s):  
Skeletal Muscle ◽  
Molecular Analysis ◽  
Intermediate Filaments ◽  
Intermediate Filament ◽  
Direct Evidence ◽  
Two Dimensional ◽  
Myocardial Cells ◽  
Intermediate Filament Proteins ◽  
Bovine Myocardium ◽  
Bearing Structure

Myocardial cells contain a cytoskeleton of intermediate filaments connecting the myofibrils. The present molecular analysis of the myocardial cytoskeleton was designed to identify the intermediate filament proteins and examine their assembly properties. The intermediate filament proteins desmin and vimentin were isolated from adult bovine myocardium by sequential extraction, urea solubilization, and chromatography on hydroxylapatite and DEAE columns. Desmin was obtained virtually pure in one peak and in a mixture of desmin and vimentin in the trailing fractions. Intermediate filaments of different morphologies polymerized in the desmin and the desmin-vimentin fractions. Isolated myocardial desmin occurs as three isozymes and isolated myocardial vimentin as two isozymes, which co-migrate on two-dimensional gels with corresponding isozymes from bovine skeletal and smooth muscle. Polypeptides of 200,000 and 220,000 daltons that fractionate with myocardial desmin and vimentin are also present in cytoskeletons of smooth and skeletal muscle. The results provide direct evidence that myocardial desmin can assemble to form intermediate filaments, suggesting that desmin is the major component of the cytoskeletal filaments in cardiomyocytes.

To bead or not to bead? Lens-specific intermediate filaments revisited

1997 ◽  
Vol 110 (21) ◽  
pp. 2629-2634 ◽  
Author(s):  
S.D. Georgatos ◽  
F. Gounari ◽  
G. Goulielmos ◽  
U. Aebi
Keyword(s):  
Plasma Membrane ◽  
Intermediate Filaments ◽  
Cultured Cells ◽  
Fiber Cells ◽  
New Information ◽  
Specific Proteins ◽  
Beaded Filaments ◽  
Nodular Appearance

For nearly three decades cytoplasmic intermediate filaments (IFs) have been described as 10 nm thick, unbranched ropes radiating from the cell nucleus and extending to the plasma membrane. This stereotype is now being challenged by the discovery and molecular characterization of the beaded filaments (BFs), a novel class of IFs composed of the lens-specific proteins filensin and phakinin. In contrast to ‘mainstream’ IFs, BFs have a distinctly nodular appearance and form a meshwork underneath the plasma membrane of the lens fiber cells. In vitro assembly studies, expression of filensin and phakinin in cultured cells, and analysis of the corresponding genes reveal that these proteins have evolved from two different subfamilies of IF proteins, thus yielding a unique structure. The new information provides a basis for understanding how the various forms of tissue-specific IF proteins might have developed adopting to the constraints of a specialized environment.

Controlling skeletal muscle CPT-I malonyl-CoA sensitivity: the importance of AMPK-independent regulation of intermediate filaments during exercise

2017 ◽  
Vol 474 (4) ◽  
pp. 557-569 ◽  
Author(s):  
Paula M. Miotto ◽  
Gregory R. Steinberg ◽  
Graham P. Holloway
Keyword(s):  
Skeletal Muscle ◽  
Intermediate Filaments ◽  
Intermediate Filament ◽  
Lipid Transport ◽  
Palmitoyl Carnitine ◽  
Malonyl Coa ◽  
Mitochondrial Lipid ◽  
Cpt I ◽  
Amp Activated Protein Kinase

The obligatory role of carnitine palmitoyltransferase-I (CPT-I) in mediating mitochondrial lipid transport is well established, a process attenuated by malonyl-CoA (M-CoA). However, the necessity of reducing M-CoA concentrations to promote lipid oxidation has recently been challenged, suggesting external regulation on CPT-I. Since previous work in hepatocytes suggests the involvement of the intermediate filament fraction of the cytoskeleton in regulating CPT-I, we investigated in skeletal muscle if CPT-I sensitivity for M-CoA inhibition could be regulated by the intermediate filaments, and whether AMP-activated protein kinase (AMPK) could be involved in this process. Chemical disruption (3,3′-iminodipropionitrile, IDPN) of the intermediate filaments did not alter mitochondrial respiration or sensitivity for numerous substrates (palmitoyl-CoA, ADP, palmitoyl carnitine and pyruvate). In contrast, IDPN reduced CPT-I sensitivity for M-CoA inhibition in permeabilized muscle fibers, identifying M-CoA kinetics as a specific target for intermediate filament regulation. Importantly, exercise mimicked the effect of IDPN on M-CoA sensitivity, suggesting that intermediate filament disruption in vivo is physiologically important for CPT-I regulation. To ascertain a potential mechanism, since AMPK is activated during exercise, AMPK β1β2-KO mice were utilized in an attempt to ablate the observed exercise response. Unexpectedly, these mice displayed drastic attenuation in resting M-CoA sensitivity, such that exercise and IDPN could not further alter M-CoA sensitivity. These data suggest that AMPK is not required for the regulation of the intermediate filament interaction with CPT-I. Altogether, these data highlight that M-CoA sensitivity is important for regulating mitochondrial lipid transport. Moreover, M-CoA sensitivity appears to be regulated by intermediate filament interaction with CPT-I, a process that is important when metabolic homeostasis is challenged.

Transient expression of the intermediate filament nestin during skeletal muscle development

1993 ◽  
Vol 106 (4) ◽  
pp. 1291-1300 ◽  
Author(s):  
T. Sejersen ◽  
U. Lendahl
Keyword(s):  
Skeletal Muscle ◽  
Transient Expression ◽  
Intermediate Filaments ◽  
Intermediate Filament ◽  
Muscle Development ◽  
Skeletal Muscle Development ◽  
Adult Rat ◽  
Before And After ◽  
Filament Network

It has previously been established that skeletal muscle development is accompanied by changes in the composition of intermediate filaments: vimentin is expressed predominantly in myoblasts and desmin in adult myotubes. We show that the intermediate filament transitions during muscle development are more complex, and involve a transient expression of the recently discovered intermediate filament nestin. Nestin RNA is expressed predominantly early, in a biphasic pattern, and is markedly downregulated in adult rat muscle, whereas desmin RNA becomes more abundant throughout development. Nestin protein was found up to the postnatal myotube stage, where it colocalized with desmin in Z bands. The intracellular distribution of nestin, vimentin and desmin was analysed in the human myogenic cell line G6 before and after in vitro differentiation. Despite its more distant evolutionary and structural relationship to the other two intermediate filaments, nestin formed a cytoplasmic filamentous network indistinguishable from that of desmin and vimentin, both in undifferentiated myoblasts and after differentiation to multinuclear myotubes. In conclusion, our data suggest that nestin is an integrated component of the dynamic intermediate filament network during muscle development and that nestin copolymerizes with desmin and vimentin at stages of coexpression.

Direct involvement of a lamin-B-related (54 kDa) protein in the association of intermediate filaments with the postsynaptic membrane of the Torpedo marmorata electrocyte

1995 ◽  
Vol 108 (1) ◽  
pp. 153-160
Author(s):  
A. Cartaud ◽  
B.J. Jasmin ◽  
J.P. Changeux ◽  
J. Cartaud
Keyword(s):  
Acetylcholine Receptor ◽  
Intermediate Filaments ◽  
Intermediate Filament ◽  
Early Stage ◽  
Postsynaptic Membrane ◽  
Muscle Fibres ◽  
Motor Innervation ◽  
Torpedo Marmorata ◽  
Lamin B ◽  
Stage Of Development

Mechanisms by which motor innervation induces postsynaptic membrane differentiation and functional compartmentalization of the subneural sarcoplasm in skeletal muscle fibres are still poorly understood. However, transmembrane control of cytoskeletal activities by the nerve terminal may be considered. Here, we examine several properties of a 54 kDa protein, previously identified in the postsynaptic membrane of the Torpedo marmorata electrocyte with anti-lamin B antibodies, in order to study its role in the assembly of the subneural intermediate filament meshwork. Using a ligand blot assay, we show that this protein binds desmin, a type III intermediate filaments protein, at micromolar concentrations. Moreover, purified acetylcholine receptor-rich membrane fragments are able to generate arrays of desmin filaments in vitro. Immunofluorescence experiments indicate that the 54 kDa protein becomes associated with the acetylcholine receptor-rich membrane at an early stage of development of the electrocyte, and that a polarized desmin network develops concomitantly from the postsynaptic membrane. Taken together, these data show that, like karyoskeletal lamin B, the 54 kDa protein is involved in the organization of the subneural intermediate filament meshwork. Control of the assembly of the subneural cytoskeleton by components of the postsynaptic membrane may thus be a prerequisite for the functional compartmentalization of the muscle fibre triggered by motor innervation.

scholarly journals Modulation of desmin intermediate filament assembly by a monoclonal antibody.

1988 ◽  
Vol 106 (3) ◽  
pp. 735-745 ◽  
Author(s):  
W Ip
Keyword(s):  
Monoclonal Antibody ◽  
Electron Microscope ◽  
Intermediate Filaments ◽  
Intermediate Filament ◽  
Building Blocks ◽  
Trypsin Digestion ◽  
Amino Terminal ◽  
The Core ◽  
Filament Assembly ◽  
Different Diameters

We have used a monoclonal antibody against desmin to examine the assembly of intermediate filaments (IF) from their building blocks, the tetrameric protofilaments. The antibody, designated D76, does not cross react with any other IF proteins (Danto, S.I., and D.A. Fischman. 1984. J. Cell Biol. 98:2179-2191). It binds to a region amino-terminal to cys-324 of avian desmin that is resistant to chymotrypsin and trypsin digestion, and in the electron microscope appears to bind to the ends of tetrameric protofilaments. In combination, these findings suggest that the epitope of the antibody resides at the amino-terminal end of the alpha-helical rod domain. Preincubation of desmin protofilaments with an excess of D76 antibodies blocks their subsequent assembly into IF. In the presence of sub-stoichiometric amounts of antibodies, IF are assembled from protofilaments but they are morphologically aberrant in that (a) they are capped by IgG molecules at one or both ends; (b) they are unraveled to varying degree, revealing a characteristic right-handed helical arrangement of sub-filamentous strands of different diameters. The antibody binds only to the ends but not along the length of desmin IF. The most straightforward explanation for this is that the epitope resides in a part of the desmin molecule that becomes buried within the core of the filament upon polymerization and is therefore inaccessible to the antibody.

scholarly journals Presuppositions, implicatures, and contextual equivalence

2021 ◽  
Author(s):  
Paul Marty ◽  
Jacopo Romoli
Keyword(s):  
Linguistic Theory ◽  
Empirical Adequacy ◽  
The Novel ◽  
Systematic Comparison ◽  
The Core ◽  
New Information ◽  
Maximize Presupposition ◽  
Important Challenge ◽  
Contextual Equivalence

AbstractMaximize Presupposition! (MP), as originally proposed in Heim (Semantik: Ein internationales Handbuch der zeitgenössischen Forschung, pp. 487–535, 1991) and developed in subsequent works, offers an account of the otherwise mysterious unassertability of a variety of sentences. At the core of MP is the idea that speakers are urged to use a sentence ψ over a sentence ϕ if ψ contributes the same new information as ϕ, yet carries a stronger presupposition. While MP has been refined in many ways throughout the years, most (if not all) of its formulations have retained this characterisation of the MP-competition. Recently, however, the empirical adequacy of this characterisation has been questioned in light of certain newly discovered cases that are infelicitous, despite meeting MP-competition conditions. This has led some researchers to broaden the scope of MP, extending it to competition between sentences which are not contextually equivalent (Spector and Sudo in Linguistics and Philosophy 40(5):473–517, 2017) and whose presuppositions are not satisfied in the context (Anvari in Proceedings of Semantics and Linguistic Theory 28, pp. 711–726, 2018; Manuscript, IJN-ENS, 2019). In this paper, we present a body of evidence showing that these formulations of MP are sometimes too liberal, sometimes too restrictive: they overgenerate infelicity for a variety of felicitous cases while leaving the infelicity of minimally different cases unaccounted for. We propose an alternative, implicature-based approach stemming from Magri (PhD dissertation, MIT, 2009), Meyer (PhD dissertation, MIT, 2013), and Marty (PhD dissertation, MIT, 2017), which reintroduces contextual equivalence and presupposition satisfaction in some form through the notion of relevance. This approach is shown to account for the classical and most of the novel cases. Yet some of the latter remain problematic for this approach as well. We end the paper with a systematic comparison of the different approaches to MP and MP-like phenomena, covering both the classical and the novel cases. All in all, the issue of how to properly restrict the competition for MP-like phenomena remains an important challenge for all accounts in the literature.

Lexical Arguments and Information Types in Malay Oral Narratives

2015 ◽  
Vol 7 (1) ◽  
pp. 80-97
Author(s):  
Siaw-Fong Chung
Keyword(s):  
Information Flow ◽  
The Other ◽  
Discourse Structure ◽  
Oral Narratives ◽  
Clear Cut ◽  
The Core ◽  
New Information ◽  
Intonation Units ◽  
Locative Expressions ◽  
Transitive Verbs

The analysis in this paper was based on five Malay narratives of the “frog story”. In these narratives, the types of lexical arguments and their relations with information flow and topic continuity were analyzed. It was found that most narrators used one lexical argument in telling the frog story (e.g., sarang itu jatuh “the nest fell”). About 60% of the verbs in the narratives contained one lexical argument only. Some transitive verbs that usually require the presence of both lexical arguments were used with one lexical argument only when produced in speech (e.g., dia mencari ø di merata tempat “he searched (for) ø everywhere”). Objects were sometimes omitted, as their meanings could be predicted from previous context. Despite the omission of objects, transitive constructions still prevailed in the stories. The most frequently occurring lexical arguments were objects (O) (37%), followed by intransitive subjects (S) (29%) and transitive subjects (A) (27%). In addition, our results showed that new information in Malay was usually allocated to the core argument of the object and to locative expressions, indicating that most of the new information appeared at the end of a clause. On the other hand, topic continuity was held between the subjects in two continuous intonation units. This clear-cut division of discourse functions in the heads and tails of constructions was consistently found in the five pieces of narration. This observation not only showed how ideas could be continued in Malay oral narratives, but also contributes to the study of discourse structure in Malay.

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